This invention relates to the extraction of nickel from nickel-bearing ores and in particular to the selective extraction of nickel from nickel-bearing ores having a high magnesia/low iron oxide content in which the nickel is in the form of oxide and/or silicate salts.
Processes for the leaching of nickel oxide/silicate ores are known. Such ores may be subjected to a prereduction process followed by an ammonia leaching process, for example, using ammonia/ammonium carbonate solutions. In an ammonia leaching process, magnesium salts may contaminate the leaching solution and result in a scaling problem in subsequent steps in the process. The scaling problem is discussed in U.S. Pat. No. 3,644,114 of E. A. Vosahlova et al. which issued on Feb. 22, 1972. Acid leaching of ores having a high iron content is also known but application of an acid leaching process to a high magnesia ore may result in undesirable dissolution of magnesium. Nickel may also be extracted from nickel-bearing ores using pyrometallurgical processes.
The use of polyamine extraction processes is also known. J. D. Watson, Sr. et al. in Canadian Pat. No. 890,347 which issued Jan. 11, 1972, describe a process for the chemical extraction of nickel, copper, chromium and cobalt metal values from ores. The process comprises contacting the ore with an aqueous solution of a polyalkylene-polyamine or polyalkyleneimine, or mixtures thereof. One of the examples illustrates the selective extraction of cobalt and chromium from a low magnesia/high iron oxide ore containing nickel using an aqueous polyethylenehexamine solution.
It has now been found that nickel may be extracted from high magnesia/low iron oxide ore using an aqueous solution of polyalkylenehexamine.